Answer:
ierror(VLOOKUP(Q2,CBFStaff[[Staff ID]:[Name]],2,FALSE), "Invalid Staff ID")
Explanation:
Let me try as much as I can to explain the concept or idea of iferror in vlookup.
iferror have a typically function and result like an if else statement, its syntax is IFERROR(value,value _ if _ error), this simply means that if the the error is equal to value, value is returned if not, the next argument is returned.
Having said that, feom the question we are given,
let's substitute the value with vlookup function and add an else argument, it will look exactly this way;
IFERROR(VLOOKUP(),"Invalid Staff ID")// now this will set the message if vlookup cannot find the.
On the other hand using the values given, we will have;
ierror(VLOOKUP(Q2,CBFStaff[[Staff ID]:[Name]],2,FALSE), "Invalid Staff ID")